66 строки
1.9 KiB
C++
66 строки
1.9 KiB
C++
// Copyright 2013 The Emscripten Authors. All rights reserved.
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// Emscripten is available under two separate licenses, the MIT license and the
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// University of Illinois/NCSA Open Source License. Both these licenses can be
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// found in the LICENSE file.
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#include <stdio.h>
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#include "emscripten.h"
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#ifndef REPORT_RESULT
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// To be able to run this test outside the browser harness in node.js/spidermonkey:
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#define REPORT_RESULT(result)
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#endif
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int result = 0;
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const double good_enough = 5.0; // good as we can do, given spectre...
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int main() {
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// This code tests three things:
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// a) Calling emscripten_get_now(), time actually proceeds.
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// b) Values returned by emscripten_get_now() are strictly nondecreasing.
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// c) emscripten_get_now() is able to return sub-millisecond precision timer values.
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double smallest_delta = 1000.f;
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double start = emscripten_get_now();
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while (1) { // Have several attempts to find a good small delta, i.e. give time to JS engine to warm up the code and so on.
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double t = emscripten_get_now();
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if (t - start >= 5000) {
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printf("We waited long enough, %f ms\n", t - start);
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break;
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}
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double t2 = t;
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while (t2 == t) {
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t2 = emscripten_get_now();
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}
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double delta = t2 - t;
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if (delta < 0.) { // Timer must be monotonous.
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printf("Timer is not monotonous!\n");
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REPORT_RESULT(0);
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return 1;
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}
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if (delta < smallest_delta) {
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smallest_delta = delta;
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if (delta <= good_enough) {
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break;
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}
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}
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}
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if (smallest_delta <= 0.) {
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printf("Smallest delta is invalid %f\n", smallest_delta);
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REPORT_RESULT(0);
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}
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printf("Timer resolution (smallest delta): %.20f msecs\n", smallest_delta);
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if (smallest_delta <= good_enough) {
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printf("Timer resolution is good (or as good as spectre allows...).\n");
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result = 1;
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} else {
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printf("Error: Bad timer precision, too large\n");
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result = 0;
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}
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REPORT_RESULT(result);
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return 0;
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}
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